@book{s7-200-manual,
        author = "Siemens",
        title = "S7-200 Programmable Controller System Manual",
        publisher = "Siemens",
        address = "",
        year = "2003"
}

@unpublished{cg_Coq_PLC,
        author = "Gang Chen",
        title = "The Verification and Analysis of PLC Programs Using Coq Proof Assistant",
        note = "Research Report RPT-2008-1, available at
        \texttt{www.lingcore.com/reports.html}",
}

@book{CoqArt,
        author = "Bertot, Yves and Cast\'eran, Pierre",
        title = "Interactive Theorem Proving and Program Development Coq'Art: The Calculus of Inductive Constructions",
        publisher = "Springer",
        year = "2004"
}
